Typically, when a position to be measured on the surface of a rotating object is closer to a rotating center, points to be sampled are usually closer to each other, and when a position to be measured is father from the rotating center, points to be sampled are usually apart from each other more. This causes that the distribution of points to be sampled is not even on the surface of the object. That is, a typical conventional method of measuring objects in rotation may not provide even sampling the surface of an object, so the surface state of the surface of the object may be inaccurate or may be insufficient to further analyze the surface of the object.
For example, the chemical mechanical polishing (CMP) technology is mostly used in modern technologies to smooth semiconductor wafers' surfaces. For most of CMP devices, a polishing pad in rotation usually moves relative to a semiconductor wafer in order to smooth the surface of the semiconductor wafer. Therefore, in such a chemical-mechanical polishing technology, the roughness of the surface of a polishing pad will affect the quality of smoothing a semiconductor wafer's surface. Therefore, it requires a manner to evenly sample a surface of a polishing pad in rotation. Through this manner, technical personnel can well handle the surface state of a polishing pad, the efficiency of the CMP technology will be greatly enhanced, and the cost of polishing semiconductor wafers will also be controlled well.